When you manually deactivate a user it doesn’t automatically send an email asking them to revalidate, though you can press the button that appears in their user/admin page to resend one.
When an inactive account attempts to login they should be prompted with a screen like this where they can choose to have a fresh one sent:
I’m not sure why your screenshot seems to be missing that option? Could it be some custom code you’ve added to hide a particular button that has also accidentally hidden this one? Does it show up in safe mode?
Edit: After a little bit of digging, I think it’s the must approve users
setting that makes the box disappear. When I enable that I no longer get the option showing up:
I’m not 100% sure that’s intentional.